1. Field of the Invention
The present invention relates to toll telephone systems and methods, and particularly relates to such systems and methods which are programmable to provide certain desirable features, such as local toll-free calling with no special equipment or modification to central office equipment.
2. Description of the Prior Art
Typical telephone systems utilized tip and ring conductors between a central office and each telephone station to permit the flow of various signals between the central office and the telephone. In the case of a coin trunk, the central office provides certain signals for requiring the deposit of a coin before completing the local call.
In order to accomplish these various functions, prior art telephone systems have utilized multiple coin control relays, as well as a coin escrow relay to respond to the various toll signals from the central office.
It is known in the prior art to program a central office and to permit certain limited toll-free calls from a coin telephone. Among these are calls for operator assistance, emergency telephone calls and the like. However, such coin-free calling has heretofore relied on specific digit combinations for the number being called or the prefix thereto and was done in the central office.